1. Technical Field
The embodiments herein generally relate to microelectronic devices and fabrication methods and, more particularly, to gallium nitride semiconductor devices and fabrication methods thereof.
2. Description of the Related Art
Gallium nitride is being widely investigated for microelectronic devices including but not limited to transistors, field emitters, and optoelectronic devices. It will be understood that, as used herein, gallium nitride also includes alloys of gallium nitride such as aluminum gallium nitride, indium gallium nitride and aluminum indium gallium nitride.
A major problem in fabricating gallium nitride-based microelectronic devices is the fabrication of gallium nitride semiconductor layers having low defect densities. It is known that contributors to defect density are the lattice and thermal mismatch between the substrate and the gallium nitride layer. Accordingly, although gallium nitride layers have been grown on sapphire substrates, it is possible to reduce defect density by growing gallium nitride layers on aluminum nitride buffer layers which are themselves formed on silicon carbide substrates.